Air filters are well known devices in which an air stream is drawn or forced into a housing and caused to pass through a filter media configured to remove dirt, dust and other particles entrained in the air stream. The air stream cleaned by the filter is thereafter used in devices such as internal combustion engines.
The filter element is disposed in a filter retainer or housing between an air inlet and air outlet. Generally, the seal is positioned to seal the air inlet from the air outlet so that all air passing out of the outlet has been passed through the filter element. For most automotive applications, the filter element is conveniently constructed of pleated paper with pleats facing upstream toward the air stream inlet and downstream toward the air stream outlet. These filters may be of a panel, radial or frusto-conical configuration. Many light duty air filters used in automotive applications to filter inlet air for internal combustion engines are configured as rectangular panels to filter the high velocity air consumed by the engines.
There is a continuing effort to improve the performance and efficiency of air filters by reducing restriction to air flow so as to enhance fuel consumption and engine power while encouraging laminar air flow and increasing capacity and thus the useful life of air filters.